1. Field of the Invention
The present invention relates to a duplexer module including a duplexer that is disposed on a printed board or a multilayer substrate.
2. Description of the Related Art
A duplexer module for separating a transmission signal and a reception signal is included in a front-end unit, such as a cellular phone. In general, a duplexer module is mounted on a mount device, e.g., a printed board, by using mounting electrodes formed on a mounting surface of a module substrate. Further, discrete components are mounted to surface electrodes formed on a chip mounting surface of the module substrate. The mounting electrodes and the surface electrodes are connected through a via holes filled with a conductive material, and pattern electrodes. A transmission filter and a reception filter are disposed respectively in a transmission line and a reception line.
A duplexer module including a plurality of duplexers adapted for different target signal frequency bands is often utilized in a multi-band front-end unit (see, e.g., Japanese Unexamined Patent Application Publication No. 2005-123909). In that type of duplexer module, each duplexer is constituted as a discrete component in which a transmission filter and a reception filter are integrated with each other. The discrete components including the duplexers are arranged adjacent to each other in such a state that respective input terminals are oriented in the same direction and respective output terminals are also oriented in the same direction.
With repeated reduction in the size of the duplexer module, it becomes difficult to arrange a transmission line through which a transmission signal passes and a reception line through which a reception signal passes, while still being able to maintain a sufficient spacing between both the lines. In the multi-band adapted duplexer module mentioned above, particularly, interconnection lines for individual duplexers have to be arranged in a partially crossing relationship and isolation between signal lines tends to deteriorate in some cases. In particular, when a discrete component including a transmission filter and a reception filter in an integrated state is used, the transmission filter and the reception filter are positioned closer to each other, and isolation between signal lines in which the transmission filter and the reception filter are inserted, respectively, tends to deteriorate.